The present invention relates to the preparation of organic isocyanates. More particularly, this invention relates to the preparation of organic isocyanates by the thermal decomposition of alkyl carbamates dissolved in a solvent which also acts as a catalyst with respect to the decomposition reaction.
Organic isocyanates are useful chemical intermediates. In particular, aromatic diisocyanates are important intermediates because they can be reacted with polyols to produce polyurethanes. A U.S. Pat. No. 3,962,302 shows that alkyl carbamates can be thermally decomposed to isocyanates in the absence of a solvent, but the product selectivity of this process is too low to make it successful commercially. In addition, the patent shows that inert solvents for the carbamates can be used to improve on the product selectivity of the thermal decomposition reaction. However, the rate of decomposition to the isocyanates is relatively slow when inert solvents are used.